The present invention relates to a liquid filled vibration isolator for use in, for example, an engine mount of a car body.
Hitherto, a liquid filled vibration isolator of the above-described type has been configured, for example, as shown in FIGS. 12 to 14. The liquid filled vibration isolator includes an inner cylindrical metal member 1 and a cylindrical intermediate metal member 2. The intermediate metal member 2 is disposed around the inner cylindrical metal member 1 at a distance spaced apart from the inner cylindrical metal member 1. The inner cylindrical metal member 1 and the cylindrical intermediate metal member 2 are coaxially disposed. The cylindrical intermediate metal member 2 has a pair of ring portions 2a, disposed at the two axial ends of the cylindrical intermediate metal member 2, and a connecting portion 2b for integrally connecting the ring portions 2a to each other. The connecting portion 2b has a cross section formed in a circular-arc-like shape, the cross section being a cross section in a direction perpendicular to the radial connecting portion 2b axis. The diameter of the connection portion 2b is smaller than the diameter each of the ring portions 2a. The connection portion 2b has one opening 2c formed in a direction in which main vibrations are input. A cylindrical rubber member includes a pair of side walls 3a for connecting the two axial directional ends of the cylindrical intermediate metal member 2 and the inner cylindrical metal member 1 to one another. Moreover, the rubber member includes an arm portion 3b extending between the side walls 3a at a position on the inside of the connection portion 2b in the axial direction. Thus, the arm portion 3b connects the connection portion 2b and the inner cylindrical metal member 1 to each other. The rubber member has a thin diaphragm portion 3c disposed on the outside of the connection portion 2b such that a gap 3d is created between the connection portion 2b and the thin diaphragm portion 3c. The diaphragm portion 3c extends between two opposite side portions in the axial direction of the liquid filled vibration isolator. In addition, the rubber member has a recess 3e surrounded by the pair of side walls 3a and the arm portion 3b and the recess 3e is opened in the opening 2c. A passage forming member 4 joins the pair of ring portions 2a. The passage forming member 4 closes the opening 2c in the connection portion 2b and has a shape extending on the two sides in the circumferential direction.
As shown in FIG. 15A, the passage forming member 4 includes a circular-arc plate 4a having a width slightly larger than the opening 2c in a part of the connection portion 2b. Moreover, a plurality of partition walls 4b are disposed on the outside of the circular-arc plate 4a at positions between the two sides thereof (the two sides included) in the widthwise direction such that the distances between the partition walls 4b are substantially the same and the partition walls 4b alternately extend from each of the two ends of the circular-arc plate in the circumferential direction. Moreover, end walls 4c stand erect at the two ends of the circular-arc plate 4a in the circumferential direction. Thus, a reciprocative passage 4d is formed. The reciprocative passage 4d reciprocates between the two ends of the circular-arc plate 4a in the circumferential direction. Referring to FIG. 15A, a first communication opening 5a, which is allowed to communicate with the recess 3e, is formed at a first end of the reciprocative passage and a second communication opening 5b, which is allowed to communicate with the gap 3d, is formed at a second end of the reciprocative passage 4d. As shown in FIG. 13, an upper stopper member 6a, made of rubber to have elasticity, is molded on the reverse side of the passage forming member 4 by vulcanization. A lower stopper member 6b is disposed on the inside of the upper stopper member 6a an is made of resin.
An outer cylindrical metal member 7, which includes a rubber seal 7a on the inner surface thereof, is coaxially disposed on the outside of the cylindrical intermediate metal member 2. The outer cylindrical metal member 7 is being secured to the cylindrical intermediate metal member 2 via drawing process. The outer cylindrical metal member 7 closes the space from the cylindrical intermediate metal member 2 in a fluid-tight manner so that a main liquid chamber 8a is formed in the recess and a sub-liquid-chamber 8b is formed in the gap 3d. In addition, an orifice passage 8c is formed in a space within the passage forming member 4 to allow the main liquid chamber 8a and the sub-liquid-chamber 8b to communicate with each other.
When in use, the inner cylindrical metal member 1 of the liquid filled vibration isolator is connected to a support member (not shown) of a car body and the outer cylindrical metal member 7 is connected to a support member (not shown) adjacent to the engine of the car. The upper and lower stopper members 6a, 6b are disposed in the vertical direction (i.e., the direction in which the main vibrations of the engine are input). In addition, the main liquid chamber 8a and the sub-liquid-chamber 8b are disposed in the vertical direction across the inner cylindrical metal member 1. If vibrations are produced between the inner cylindrical metal member 1 and the outer cylindrical metal member 7, the elastic action of the rubber member and the resonant action of the liquid column (i.e., via liquid which flows in the orifice passage 8c) damp the vibrations.
Since the passage forming member 4 of the liquid filled vibration isolator is made of metal, such as an aluminum die-cast, a problem arises in that the weight of the liquid filled vibration isolator becomes heavier as the absolute length of the orifice passage is elongated. The passage forming member 4, joined to the cylindrical intermediate metal member 2, is immersed in a liquid to fill the inside portion of the recess 3e and similar the liquid. Then, the outer cylindrical metal member 7, disposed on the outer surface of the cylindrical intermediate metal member 22 is subjected to the drawing process in the liquid. Since only one opening (i.e., the communication opening) of the passage forming member 4, which is allowed to communicate with the recess 3e, is provided, air in the main liquid chamber 8a cannot easily be discharged. Thus, a long time is required to complete the liquid filling operation. Another problem arises in that residual air in the main liquid chamber 8a deteriorates the performance for isolating vibrations.
To overcome the foregoing above-described problems, an object of the present invention is to provide a liquid filled vibration isolator which can easily and reliably be filled with liquid and which enables the weight of a passage forming member thereof to be reduced.
To achieve the foregoing object, according to one aspect of the present invention, a liquid filled vibration isolator comprising: an inner cylindrical metal member; a cylindrical intermediate metal member disposed on the outside of the inner cylindrical metal member at a position apart from the inner cylindrical metal member and incorporating paired ring portions formed at two ends in the axial direction, a connection portion for integrally connecting the paired ring portions to each other and an opening formed in a direction in which main vibrations are input; a rubber member constituted by paired side wall portions for connecting the paired ring portions of the intermediate metal member and the inner cylindrical metal member to each other, an arm portion for connecting the paired side wall portions in an axial direction to connect the connection portion and the inner cylindrical metal member, a recess surrounded by the paired side wall portions and the arm portion and opened in the opening, a thin diaphragm portion disposed opposite to the opening in a radial direction such that the thin diaphragm portion is disposed apart from the inner cylindrical metal member and the arm portion at a position between the paired ring portions of the intermediate metal member, and a rubber sealing portion disposed on the outer surface of the cylindrical intermediate metal member; a passage forming member incorporating a circular-arc plate disposed on the outside of the connection portion and extending in the circumferential direction to close the opening, a reciprocative passage groove formed in the outer surface of the circular arc plate to reciprocate between two ends in the circumferential direction, a first communication opening allowed to communicate with the recess at one end of the reciprocative passage groove and a second communication opening opened in the circumferential direction at another end of the reciprocative passage groove; and an outer cylindrical metal member secured to the outside portion of the cylindrical intermediate metal member and the passage forming member, arranged to cause the sealing portion to close a space from the cylindrical intermediate metal member in a liquid-tight manner to form a main liquid chamber in the recess; and a sub-liquid-chamber defined by the diaphragm portion and capable of forming an orifice passage in a space from the passage forming member to allow the main liquid chamber and the sub-liquid chamber to communicate with each other, wherein the reciprocative passage groove, which is formed into the orifice passage, is formed by at least one partition wall extending from either end of the circular-arc plate in the circumferential direction, except for the two ends of the circular-arc plate in the widthwise direction and end walls standing erect at two ends of the circular-arc plate in the circumferential direction. When a plurality of the partition walls, are provided, the partition walls disposed at substantially the same distances in the widthwise direction, are alternately extended from the two ends of the circular-arc plate in the circumferential direction, except for the two ends of the circular-arc plate in the widthwise direction.
In the present invention configured as described above, no partition wall is disposed at the two ends of the passage forming member in the widthwise direction. But in the passage forming member having no partition wall at its widthwise ends a passage can be formed between the other partition wall on the inside in the widthwise direction and the inside portions of the ring portion of the cylindrical intermediate metal member in the axial direction. Therefore, both a long passage, having an appropriate width, and the vibration isolating function, of the orifice passage of the liquid filled vibration isolator, can be maintained. Moreover ,since no partition wall is disposed at the two ends in the axial direction, the weight and manufacturing cost of the passage forming member can be reduced.
An air discharging opening, which penetrates the partition wall in the radial direction and which is allowed to communicate with the recess, may be provided for a portion of the partition wall. Since the air discharging opening is formed in a portion of the partition wall of the passage forming member, removal of a bubble in the main liquid chamber can easily and reliably be performed through the air discharging opening when an operation for filling the recess with liquid is performed. Since the air discharging opening is provided for a portion of the partition wall, the width of the passage (i.e., formed, as described above, between the partition on the inside of the widthwise direction and the inside portion of the ring portions of the cylindrical intermediate metal member in the axial direction), of the passage forming member, is reduced in the foregoing portion of the partition wall. However, omission of the partition wall at the two ends of the passage forming member in the widthwise direction enables preventing a reduction in the width of the passage.
A configuration may be employed in which a projection, projecting outwardly in the radial direction, is provided for a portion of the reciprocative passage groove, and an air discharging opening, which penetrates the projection in the radial direction and which is allowed to communicate with the recess, is provided for the projection. Since the air discharging opening is formed in the projection provided for a portion of the reciprocative passage of the passage forming member, removal of a bubble in the main liquid chamber can easily and reliably be performed through the air discharging opening when an operation for filling the recess with liquid is performed. Since the projection is provided for a portion of the reciprocative passage, the width of the passage (i.e., formed, as described above, between the partition on the inside of the widthwise direction and the inside portion of the ring portions of the cylindrical intermediate metal member in the axial direction), of the passage forming member, is reduced in the foregoing portion. However, omission of the partition wall at the two ends of the passage forming member in the widthwise direction enables preventing a reduction in the-width of the passage.
A passage forming recess, which is allowed to communicate with the reciprocative passage groove, may be provided for a portion of the cylindrical intermediate metal member opposite to the air discharging opening in the axial direction. Therefore, either the air discharging opening, provided for a portion of the partition wall, or the projection causes the width of the passage (i.e., formed, as described above, between the partition on the inside of the widthwise direction and the inside portion of the ring portions of the cylindrical intermediate metal member in the axial direction), of the passage forming member, to be reduced. However the passage forming recess, provided for the corresponding position of the cylindrical intermediate metal member, enables the width of the reciprocative passage in the narrowed portion to be enlarged relatively.